Papers by Author: Zhi Jian Pei

Abstract: Sapphire, widely used in high-speed integrated-circuit chips, thin-film substrates, and various electronic components, is regarded as one of the most difficult to cut materials owing to its great hardness and low fracture toughness. Rotary ultrasonic machining (RUM) has been regarded as an effective processing method for hard and brittle materials. In this paper, RUM process is introduced into the drilling of sapphire for the first time. The feasibility to machine sapphire using RUM is studied. Moreover, results of a designed experimental study into RUM of sapphire are presented to discuss the main effects as well as interaction effects of process parameters (ultrasonic power, spindle speed, and feedrate) on outputs. The process outputs investigated include cutting force and edge chipping size.

Abstract: As one of the cost-effective machining methods for advanced ceramics, rotary ultrasonic machining (RUM) has attracted much attention and there exist numerous publications on the process. However, few investigations on tool wear in the RUM process have been reported. This paper, for the first time in literature, presents an experimental observation on tool wear in RUM of alumina. it presents and discusses the results on tool wear in RUM of alumina. It also discusses some practical implications of the findings from this study.

Abstract: Lapping is an important material-removal process for manufacturing of substrate wafers. Objectives of lapping include removing subsurface damage in sliced wafers, thinning wafers to target thickness, and achieving a high degree of parallelism and flatness of wafer surfaces. This paper reviews the literature on lapping of substrate wafers. It presents reported experimental results on effects of input parameters (lapping pressure, plate rotation speed, abrasive grain size, slurry concentration, and slurry flow rate) on material removal rate and surface roughness.

Abstract: Rotary ultrasonic machining (RUM) is considered as an effective machining method, which has been utilized to machine hard and brittle materials such as advanced ceramics. In order to improve the hole wall surface quality during RUM, it is important to wash away swarf in the gap between the tool and the workpiece as fast as possible. In this paper, a new machine process – intermittent rotary ultrasonic machining (IRUM) – is introduced for the first time. The cutting force, surface roughness and coolant flow rate in conventional rotary ultrasonic machining (CRUM) process and IRUM process are compared. It is found that compared with CRUM, the output coolant flow rate could be increased significantly by using the IRUM method. It is also found that the surface roughness of workpiece can be improved significantly in IRUM.

Abstract: The majority of integrated circuits are built on silicon wafers. To manufacture high-quality silicon wafers, a series of processes are needed. After a wire sawing process slices silicon ingots into wafers, grinding processes can be used to flatten the sliced wafers. This paper reports three experimental investigations on wafer grinding. The first investigation was to study the effectiveness of soft-pad grinding in removing the wire-sawing induced waviness. The second was to explore the capability of grinding in achieving super flatness. The third was to study the effects of grinding parameters on wafer flatness.

Abstract: This paper reports two investigations on the edge chipping in rotary ultrasonic machining using finite element analysis (FEA). The first FEA investigation establishes a relationship between edge chipping thickness and cutting force. The second FEA investigation is to understand the effects of three parameters (cutting depth, support length, and pre-tightening load) on edge chipping thickness. The investigation results showed that the edge chipping thickness could be reduced by increasing support length and decreasing cutting force.

Abstract: Rotary ultrasonic machining (RUM) is one of the cost-effective machining methods for advanced ceramics, which is a hybrid machining process that combines the material removal mechanisms of diamond grinding and ultrasonic machining (USM). This paper presents an overview of the investigations on RUM of advanced ceramics. The issues about the material removal mechanisms, process modeling, material removal rate, and tool wear in RUM are reviewed. Directions of future research on RUM are also presented.